Nearly 10,000 ducks have died from an epidemic in duck farms in Beijing's Pinggu District, government authorities said Friday.

The municipal and district disease control departments confirmed the ducks were infected with secondary E. coli following infectious serositis, said a spokesman with municipal control headquarters of major animal and plant epidemics.

Media reports had suspected the deaths were caused by bird flu.

The ducks were found dead from April 29 in six duck farms in Shandongzhuang Township, but the farmers did not report the cases to the animal disease control department until May 6. As of Wednesday, 10,000 ducks had been reported dead.

Initial investigations found non-native duck dealers carrying the infectious virus had entered the farms to buy ducks, which later caused the epidemic, according to the spokesman.

The Pinggu District Government has launched disease control and disinfection work, and the epidemic is now under control, he said.